This invention relates to a self contained breathing apparatus.
Specifically this invention relates to a self contained breathing apparatus that provides an indication to a user that a supply of air is approaching depletion.
Self contained breathing apparatus are known in the prior art. Such devices are commonly used by individuals who are required to perform activities in noxious atmospheres. Individuals who commonly use self contained breathing apparatus include fire fighters and persons involved in cleaning up chemical spills.
A self contained breathing apparatus generally includes a supply of pressurized breathing air. The breathing air is maintained in a vessel at a relatively high pressure. Air flows from the pressure vessel to a first stage regulator which reduces the pressure from the high pressure within the vessel to a lower pressure. Air from the primary regulator is communicated to a second stage regulator. The second stage regulator is generally in communication with a face mask, hood or similar device worn by a user. The second stage regulator operates to deliver air into the face mask or hood in response to a user""s inhalation. The second stage regulator often stops the flow of air into the face mask while the user is exhaling. In this way the air supply is conserved.
A pressure vessel can supply breathing air to a user for only a limited duration. It is often desirable to warn a user that the air supply is approaching depletion so that they may leave the area with the noxious atmosphere before the supply is depleted. My prior patent, U.S. Pat. No. 3,957,044, discloses such a system. In my prior system a pair of first stage regulators set at substantially different pressures are used to supply air to a second stage regulator mounted on a user""s face mask. A pair of transfer valves are connected to the first stage regulators and to the line which supplies the second stage regulator.
In accordance with my previously developed system, when the supply of air in the pressure vessel is above a pressure which is indicative of impending depletion, the transfer valves are automatically positioned to supply air to the second stage regulator through the primary first stage regulator which is set at a first nominal pressure. However, when the pressure in the pressure vessel falls to a level which indicates that depletion of the supply is approaching, the transfer valves automatically shift so that the second stage regulator is supplied with air from the other first stage regulator which is set at a higher, second pressure. This higher pressure is sufficient to actuate an alarm device, such as a whistle or vibrating alarm device which warns the user of the impending depletion of the air supply in the pressure vessel each time the user inhales.
While my prior system is highly reliable, the use of two first stage regulators and a pair of transfer valves adds to its cost. In addition, it would be desirable to provide additional forms of warnings to a user of the impending depletion of the supply of air in the pressure vessel. This is particularly desirable for users who must work in noisy environments in which a whistle or other auditory or vibratory warning indication may not be perceived. Alternatively, an individual with a hearing impairment may benefit by having a visual or other form of indication in addition to an audible warning.
Thus there exists a need for a self contained breathing apparatus that provides a user with an indication of the impending depletion of the air supply, which provides multiple types of indications and which is more economical than prior systems.
It is an object of the present invention to provide a self contained breathing apparatus.
It is a further object of the present invention to provide a regulator for use in connection with a self contained breathing apparatus.
It is a further object of the present invention to provide a self contained breathing apparatus which provides a user with an indication that an air supply is approaching depletion.
It is a further object of the present invention to provide a self contained breathing apparatus that provides a user with multiple indications of the impending depletion of an air supply.
It is a further object of the present invention to provide a self contained breathing apparatus that is more economical to manufacture and use.
Further objects of the present invention will be made apparent in the following Best Modes for Carrying Out Invention and the appended claims.
The foregoing objects are accomplished in a preferred embodiment of the present invention by a self contained breathing apparatus that includes a pressure vessel containing a supply of breathing air. The breathing air from the pressure vessel is communicated to a first stage pressure regulator which is initially set at a nominal first pressure value. The pressure from the pressure vessel is also communicated to a step up valve. The first stage regulator delivers air at the first pressure to a second stage breathing regulator mounted on a face mask worn by a user. Air is then supplied to the face mask through the breathing regulator in response to a user""s breathing efforts.
When the pressure in the pressure vessel is above a level indicative of impending depletion, a transfer piston in the step up valve is biased by the pressure from the pressure vessel to a closed position. When the pressure in the pressure vessel falls to a level indicative of impending depletion, the pressure acting on the transfer piston in the step up valve is reduced to a level which causes the transfer piston to shift to a second position. Movement of the transfer piston causes pressure from the first stage regulator to be delivered to a charging passage. Delivery of increased pressure to the charging passage moves a step up piston which acts to change the pressure setting of the first stage regulator to a higher pressure. This increased pressure is communicated to the second stage breathing regulator.
The air supply to the second stage regulator is in fluid communication with a sensor which may be adjacent to the face mask or in another location. The increase in pressure is detected by the sensor which actuates an alarm circuit. The alarm circuit may include visual alarms such as lights, as well as audio or other alarms which provide the user with an indication of the impending depletion of the air supply. In addition, the increased pressure may also be used to actuate a whistle or vibrator of the conventional type in the mask or other location. These multiple alarm indications provide greater assurance that the user will be aware of the impending depletion of the air supply even though the user is working in a noisy or other difficult environment.